Photo from the protestors website. Denver capitol building is in the background.

Environmental groups and social-, racial- and economic justice groups marched for climate action on Saturday, April 29, 2017 in Denver and 11 other cities in Colorado. As the event began, outside temperatures were a freezing 31 degrees Farenheit. Water freezes below 32 degrees Farenheit, which is also zero degrees Celsius.

The events are among the 330 sister marches throughout the U.S. and globally to rally for public policies that recognize and seek to slow climate change. The events are also protests against President Donald Trump, who famously is a climate change denier.

"The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive," tweeted @RealDonaldTrump on November 12, 2012. The left have mocked him repeatedly for this stand.

The weather today, April 29, 2017 at 10 a.m. in Denver, Colorado's capital.

"Climate change is the most critical issue facing my generation," said Seth Maddox, one of the co-founders of People's Climate of Colorado, a new nonprofit formed to support the march.

"On the 100th day of the Trump administration, we march together to resist the undermining of environmental protections, the assault on clean water and air, and the attacks against indigenous communities, workers, people of color, immigrants, youth and students, working families, the LGBT+ community, women, and others whose rights are threatened." wrote Maddox about today's event in Denver.

Denver's march begins at 10:00 at Denver's Civic Center. Organizers say more than 20,000 people have expressed interest in attending.

Similar marches were held in Colorado Springs, Greeley, Carbondale, Steamboat Springs, Pueblo, Durango, and Pagosa Springs.